[Zope-dev] _v_ and ZEO

[Florent Guillaume]

Toby Dickenson  <tdickenson@geminidataloggers.com> wrote:
> >This reminds me of a question I had: given that (from what I understand)
> >_v_ attributes only live in the object cache of a given Zope,
> 
> True, and more accurate that I think you expected....
> 
> The issue is that one Zope has more than one ZODB object cache, even
> without ZEO. There is one per worker thread. Each cache has
> independant _v_ attributes

Ah, yes, I knew this in the back of my mind.

> Ive never looked at LDAPUserFolder so this may be irrelevant, but is
> it possible for LDAPUserFolder to validate that the cached _v_
> information is still fresh? If that validation is quicker than
> fetching a new copy then this is still an overall win.

I'm not sure there's a fast way for what LDAPUserFolder needs. Actually
the LDAP server itself does have a cache, so things should be fast
enough without caching in Zope. I'll have to try it.

> If data consistency is an absolute requirement, then you *have* to hit
> some shared storage on every transaction.

Ok.

I'll investigate clearing the _v_ caches at the end of the transaction,
using the REQUEST._hold hack mentionned earlier.


Anyway there are other problems with LDAP, seeing that there's no way to
undo a transaction on error...


Florent
-- 
Florent Guillaume, Nuxeo (Paris, France)
+33 1 40 33 79 87  http://nuxeo.com  mailto:fg@nuxeo.com